text: /* ----------------------------------------------------------------------
   * Project:      CMSIS DSP Library
   * Title:        arm_biquad_cascade_df1_init_f32.c
   * Description:  Floating-point Biquad cascade DirectFormI(DF1) filter initialization function
   *
   * $Date:        27. January 2017
   * $Revision:    V.1.5.1
   *
   * Target Processor: Cortex-M cores
   * -------------------------------------------------------------------- */
  /*
   * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
   *
   * SPDX-License-Identifier: Apache-2.0
   *
   * Licensed under the Apache License, Version 2.0 (the License); you may
   * not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an AS IS BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  #include "arm_math.h"
  
  /**
   * @ingroup groupFilters
   */
  
  /**
   * @addtogroup BiquadCascadeDF1
   * @{
   */
  
  /**
   * @details
   * @brief  Initialization function for the floating-point Biquad cascade filter.
   * @param[in,out] *S           points to an instance of the floating-point Biquad cascade structure.
   * @param[in]     numStages    number of 2nd order stages in the filter.
   * @param[in]     *pCoeffs     points to the filter coefficients array.
   * @param[in]     *pState      points to the state array.
   * @return        none
   *
   *
   * <b>Coefficient and State Ordering:</b>
   *
   * \par
   * The coefficients are stored in the array <code>pCoeffs</code> in the following order:
   * <pre>
   *     {b10, b11, b12, a11, a12, b20, b21, b22, a21, a22, ...}
   * </pre>
   *
   * \par
   * where <code>b1x</code> and <code>a1x</code> are the coefficients for the first stage,
   * <code>b2x</code> and <code>a2x</code> are the coefficients for the second stage,
   * and so on.  The <code>pCoeffs</code> array contains a total of <code>5*numStages</code> values.
   *
   * \par
   * The <code>pState</code> is a pointer to state array.
   * Each Biquad stage has 4 state variables <code>x[n-1], x[n-2], y[n-1],</code> and <code>y[n-2]</code>.
   * The state variables are arranged in the <code>pState</code> array as:
   * <pre>
   *     {x[n-1], x[n-2], y[n-1], y[n-2]}
   * </pre>
   * The 4 state variables for stage 1 are first, then the 4 state variables for stage 2, and so on.
   * The state array has a total length of <code>4*numStages</code> values.
   * The state variables are updated after each block of data is processed; the coefficients are untouched.
   *
   */
  
  void arm_biquad_cascade_df1_init_f32(
    arm_biquad_casd_df1_inst_f32 * S,
    uint8_t numStages,
    float32_t * pCoeffs,
    float32_t * pState)
  {
    /* Assign filter stages */
    S->numStages = numStages;
  
    /* Assign coefficient pointer */
    S->pCoeffs = pCoeffs;
  
    /* Clear state buffer and size is always 4 * numStages */
    memset(pState, 0, (4u * (uint32_t) numStages) * sizeof(float32_t));
  
    /* Assign state pointer */
    S->pState = pState;
  }
  
  /**
   * @} end of BiquadCascadeDF1 group
   */
  